Regulation and load modulation in a near field communication device

ABSTRACT

A near field communications (NFC) device is disclosed that load modulates and regulates a radio frequency (RF) signal. The NFC device includes a rectifier that rectifies the RF signal to provide a direct current voltage. The NFC device also includes a modulator that modulates a data signal. The modulator provides a first voltage when the data signal is at a first level and provides a second voltage when the data signal is at a second level. The NFC device utilizes a regulator to regulate and to load modulate the RF signal. The regulator adjusts an impedance based upon a comparison of the DC voltage provided by the regulator to the first voltage provided by the modulator for the data signal at the first level or to the second voltage provided by the modulator for the data signal at the second level.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.:13/093,740, filed on Apr. 25, 2011, now U.S. Pat. No. 9,026,046, whichclaims the benefit of Great Britain Application No. 1006830.2, filed onApr. 23, 2010. U.S. patent application Ser. No.: 13/093,740 isincorporated herein by reference in its entirety.

BACKGROUND

This invention relates to near field RF communicators such as activeRFID tags or transponders and, for example, to a near field RFcommunicator having a modified modulation circuit and to methods andapparatus for deriving a clock signal from a received RF signal in anactive RFID tag during modulation.

Near field RF communicators are often produced in silicon where designsproduced by multiple proprietors must co-exist. Accordingly a near fieldRF communicator may be required to operate using a data modulationsignal received from more than one source and/or from sources which usedifferent operating voltages. It is desirable to derive a clock signalfrom a received RF signal in a near field RF communicator for use indemodulation of the signal and in other internal functions of the nearfield RF communicator. The H-field strength available for coupling to anear field RF communicator is variable and may not be known in advanceand to protect a near field RF communicator from overvoltage conditionscaused RF H-field signals coupled to its antenna. Thus, there is a needto protect a near field communicator from over voltage conditions causedby RF H-field signals coupled to its antenna.

BRIEF SUMMARY OF THE INVENTION

Aspects and examples of the invention are set out in the claims andrelate to a near field RF communicator which has the advantage that itcan derive a clock signal reliably from a received RF voltage evenduring load modulation of the signal and even where the data signal tobe modulated is not controlled by the near field RF communicator.

In an aspect there is provided a near field RF communicator comprisingan antenna operable to inductively couple with the H-field of an RFsignal and a regulator to regulate an induced RF voltage in the antennaby controlling an impedance of the antenna in accordance with a datasignal, wherein the data signal comprises first and second modulationvoltages to define a modulation of the signal and wherein the regulatoris operable to control the impedance such that the induced RF voltage isnot regulated below a threshold voltage as a result of the modulation.

In an embodiment the near field RF communicator is manufactured by asemiconductor process, such as a CMOS process and the threshold voltageis based on a resolution limit of a comparator manufactured by thatprocess. In another embodiment the threshold voltage is selected basedon an expected signal to noise ratio of the induced RF voltage.

In an embodiment the regulator comprises an error amplifier arranged tocontrol the impedance. In an embodiment the error amplifier has a firstinput coupled to receive a voltage based on the induced RF voltage and asecond input is switchably coupled to receive one of a first and secondcontrol voltage based on the data signal wherein the control voltagesare different from the first and second voltages of the data signal andwherein the smaller of the first and second voltage is the thresholdvoltage such that the induced RF voltage is not regulated below thethreshold voltage as a result of the modulation.

In an aspect there is provided a field RF communicator having aninductive coupler for coupling to an H-field of an RF signal fromanother near field RF communicator in near field range to provide aninduced RF voltage and having a regulator coupled to the inductivecoupler and operable to regulate the induced RF voltage to be notgreater than one of a first and second regulated voltages to modulatethe H-Field of the RF signal in accordance with a modulation signalwherein the smaller of the first and second regulated voltages is suchthat a clock deriver is operable to derive a clock signal from theinduced RF voltage regulated to the smaller of the first and secondregulated voltages.

In an embodiment the clock deriver comprises a comparator and thesmaller of the first and second regulated voltages is selected inaccordance with the minimum voltage difference resolvable by thecomparator.

In an embodiment the regulator comprises first and second inputs,wherein the first input is arranged to receive a voltage based on theinduced RF voltage and the second input is switchable between a firstand second control voltage in accordance with the modulation signal.

In an aspect there is provided a method of load modulation in a nearfield communicator, the method comprising receiving a data signal andmodifying the data signal and modulating an impedance of an antenna ofthe near field communicator in accordance with the modified data signalwherein modifying the data signal comprises modifying it is such that anRF voltage provided by the antenna is not regulated to zero by the loadmodulation.

In an embodiment modifying the data signal comprises modifying it issuch that an RF Voltage provided by the antenna is not reduced below aminimum resolvable voltage amplitude.

In an embodiment the minimum resolvable voltage amplitude is fixed bythe process by which the near field communicator is manufactured. In anembodiment the minimum resolvable voltage amplitude is the minimumresolvable voltage amplitude of a comparator of the near fieldcommunicator. In an embodiment the minimum resolvable voltage amplitudeis the minimum resolvable voltage amplitude of a clock deriver of thenear field communicator. In an embodiment the amplitude is one of thepeak-to-peak amplitude and the root mean square amplitude. Typically, aswill be appreciated in the context of the present invention, regardlessof how they are calculated amplitude values describe the total voltageheadroom provided by a cyclic voltage excursion, in other words theamplitude is a measure of the difference between minimum and maximumvoltage in a cycle.

In an aspect there is provided a near field RF communicator having aninductive coupler for coupling to an H-field of another near field RFcommunicator in near field range to provide an induced RF voltage, aclock deriver arranged to derive a clock signal from the induced RFvoltage wherein the clock deriver requires a minimum input voltage inorder to derive a clock signal, and a modulation controller arranged tocontrol an impedance of the inductive coupler based on a modulationsignal such that the amplitude of the induced RF voltage is regulated toone of a first and second voltage level wherein the second voltage levelis selected in accordance with the minimum input voltage of the clockderiver.

Aspects and examples of the invention have the advantage that a nearfield RF communicator can operate reliably when receiving a modulationsignal from functionality which has not been designed to operate with aclock deriver.

In an embodiment the near field RF communicator is an active RFID tag.An active tag is a near field RF transponder which incorporates its ownpower supply such as a battery. In general an active tag is capable ofresponding to, but not initiating, RF communication. In one possibilityan active tag is maintained in a sleep or power saving mode until it isactivated by a ‘wake up’ signal.

BRIEF DESCRIPTION OF THE FIGURES

Preferred features of the invention will now be described in greaterdetail, by way of example only, with reference to the accompanyingdrawings in which:

FIG. 1 shows a representational diagram illustrating communicationbetween two devices comprising NFC communicators;

FIG. 2 shows a schematic view of components of an NFC communicator; and

FIG. 3 shows a load modulation circuit for use in an example of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the drawings in general, it should be understood thatany functional block diagrams are intended simply to show thefunctionality that exists within the device and should not be taken toimply that each block shown in the functional block diagram isnecessarily a discrete or separate entity. The functionality provided bya block may be discrete or may be dispersed throughout the device orthroughout a part of the device. In addition, the functionality mayincorporate, where appropriate, hard-wired elements, software elementsor firmware elements or any combination of these. The near field RFcommunicator may be provided wholly or partially as an integratedcircuit or collection(s) of integrated circuits.

Referring now specifically to FIG. 1, there is shown a representationaldiagram illustrating communication between two NFC communicationsenabled devices. In FIG. 1 the representations of the NFC communicationsenabled devices have been shown partly cut-away and the functionalityprovided by the NFC communications enabled devices illustrated by way ofa functional block diagram within the NFC communications enabled device.

As shown in FIG. 1, one NFC communications enabled device comprises amobile telephone (cellphone) 1 and the other NFC communications enableddevice comprises a portable computer 2 such as a notebook or laptopcomputer.

The mobile telephone 1 has the usual features of a mobile telephoneincluding mobile telephone functionality 10 (in the form of, usually, aprogrammed controller, generally a processor or microprocessor withassociated memory or data storage, for controlling operation of themobile telephone in combination with a SIM card), an antenna 8 forenabling connection to a mobile telecommunications network, and a userinterface 3 with a display 4, a keypad 5, a microphone 6 for receivinguser voice input and a loudspeaker 7 for outputting received audio tothe user. The mobile telephone also has a chargeable battery 11 coupledto a charging socket 12 via which a mains adapter (not shown) may beconnected to enable charging of the battery 11. The mobile telephone 1may have an alternative or additional power supply (not shown), forexample a reserve battery or emergency battery. The chargeable battery11 forms the primary power supply for the mobile telephone and NFCcommunicator 15. Given it is chargeable, it is designed to be removed atcertain times.

Similarly the portable computer 2 has the usual features of a portablecomputer including portable computer functionality 20 in the form of,usually, a processor with associated memory in the form of ROM, RAMand/or hard disk drive, one or more removable media drives such as afloppy disk drive and/or a CDROM or DVD drive, and possibly acommunications device for enabling the portable computer to connect to anetwork such as the Internet. The portable computer 2 also includes auser interface 21 including a display 22, a keyboard 23 and a pointingdevice, as shown a touchpad 24. The portable computer 2 also has achargeable battery 25 coupled to a charging socket 26 via which a mainsadapter (not shown) may be connected to enable charging of the battery25. Again the chargeable battery 25 is the primary power supply for theportable computer and NFC communicator 30.

In addition, as shown in FIG. 1, both NFC communications enabled devices1 and 2 have an NFC communicator 15 and 30. As shown, the NFCcommunicators 15 and 30 are incorporated within the larger devices and,as with the other functional bocks, may be discrete entities within thehost devices or may be provided by features dispersed throughout orintegrated within the host device or a part of the host device. Each NFCcommunicator 15 and 30 comprises NFC operational components 16 and 31for, as will be described below, enabling control of the NFCfunctionality and generation, modulation and demodulation of an RFsignal. Each NFC communicator 15 and 30 also comprises an antennacircuit 17 and 32 comprising an inductor or coil in the form of anantenna 18 and 33. The antenna circuits 17 and 32 enable an alternatingmagnetic field (H field) generated by the antenna of near field RFcommunicator 15 by transmission of an RF signal (for example a 13.56Mega Hertz signal) to be inductively coupled to the antenna of nearfield communicator 30 when that antenna is within the near field of theRF signal generated by the one near field RF communicator 15.

The NFC communicators 15 and 30 are coupled to the mobile telephonefunctionality 10 and portable computer functionality 20, respectively,to enable data and/or control commands to be sent between the NFCcommunicator and the host device and to enable user input to the NFCcommunicator. Communication between the user interface 3 and userinterface 21 with the NFC communicator 15 and the NFC communicator 30 isvia the mobile telephone functionality 10 and host device functionality20, respectively.

Each NFC communicator 15 and 30 also comprises a power provider 19 and34. The power providers 19 and 34 may be power supplies within the hostdevice or specific to the NFC communicators 15 and 30, for example abutton cell battery, or other small battery. In this case as shown bydashed lines in FIG. 1, one or both of the power providers 19 and 34comprise a coupling to derive power from the corresponding devicebattery 11 and device battery 25, i.e. the primary power supply.

It will be appreciated that FIG. 1 shows only examples of types of hostdevices. A host device may be another type of electrical device such asa personal digital assistant (PDA), other portable electrical devicesuch as a portable audio and/or video player such as an MP3 player, anIPOD®, CD player, DVD player or other electrical device. As anotherpossibility the NFC communicator 15 and the NFC communicator 3 may becomprised within or coupled to a peripheral device, for example in theform of a smart card or other secure element which may be stand alone orcomprised within or intended to be inserted into another electricaldevice. For example a SIM card for use in a mobile telephone. As afurther possibility such peripheral devices may comprise interfacingsystems or protocols such as the single wire protocol.

Also, rather than being incorporated within the host device, the NFCcommunicator 15 and the NFC communicator 30 may be associated with thehost device, for example by a wired or wireless coupling. In such acase, a housing of the NFC communicator may be physically separate fromor may be attached to the housing of the host device; in the later case,the attachment may be permanent once made or the NFC communicator may beremovable. For example, the NFC communicator may be housed within: ahousing attachable to another device; a housing portion, such as afascia of the NFC communications enabled device or another device; anaccess card; or may have a housing shaped or configured to look like asmart card. For example an NFC communicator may be coupled to a largerdevice by way of a communications link such as, for example, a USB link,or may be provided as a card (for example a PCMCIA card or a card thatlooks like a smart card) which can be received in an appropriate slot ofthe larger or host device.

In addition, one or both of the NFC communications enabled devices maybe a standalone NFC communicator, that is it may have no functionalitybeyond its NFC communications functionality.

FIG. 2 shows a functional block diagram of an NFC communications enableddevice 100 in accordance with the invention to illustrate in greaterdetail one way in which the NFC operational components of an NFCcommunications enabled device embodying the invention may beimplemented.

In this example, the NFC communications enabled device 100 comprises anNFC communicator 100 a having NFC operational components including anantenna circuit 102, power provider 104, controller 107, data store 108,signal generator 109 modulator 117 and demodulator 114.

The power provider 104 may be any one or more of the types of powerproviders discussed above. In the interests of simplicity, power supplycouplings from the power provider 104 to other components are not shownin FIG. 2.

The NFC communications enabled device 100 may or may not also have or becapable of being connected or coupled with at least one of otherfunctionality 105 (for example functionality of a host device orperipheral device such as described above) and a user interface 106.

The NFC operational components include a demodulator 114 coupled betweenthe antenna circuit 102 and the controller 107 for demodulating amodulated RF signal inductively coupled to the antenna circuit 102 fromanother near field RF communicator in near field range and for supplyingthe thus extracted data to the controller 107 for processing. Rectifier200 is coupled to provide a rectified output to regulator 310. Rectifier200 and regulator 310 are coupled to the outputs AC1 and AC2 of theantenna circuit. The regulator 310 sets or regulates a voltage supplylevel (pin voltage) and the rectifier 200 provides rectified voltage toremainder of NFC circuit. The regulator 310 sets or regulates thevoltage between the outputs AC1 and AC2 of the antenna circuit based onthe voltage supply level (pin voltage) provided by the rectifier 200. Asshown the demodulator 114 is coupled to the antenna circuit outputs AC1and AC2. As another possibility, as shown in dashed line in FIG. 2, thedemodulator may receive its input from the regulator 310. As a furtherpossibility, the demodulator 114 may receive its input from therectifier 200. In one possibility the regulator 310 regulates thevoltage between the outputs AC1 and AC2 of the antenna circuit based onthat voltage rather than the rectified voltage.

The NFC operational components include a modulator 117 coupled to thecontroller 107 and to the regulator 310 so that a modulation signal maybe applied to the regulator 31 to cause the regulator to vary the loadon the antenna circuit 102.

A clock deriver 115 is coupled to receive the voltage AC1-AC2 of theantenna circuit and to derive a clock signal from the voltage AC1-AC2and is coupled to provide the derived clock signal to the demodulator114 and can be coupled to provide the derived clock signal to any of thecontroller 107, the signal generator 109, the modulator 117 and/or otherfunctionality 105 of the near field RF communicator. Any appropriateclock derivation may be used such as, for example, a clock recovery.

Together the rectifier 200 and regulator 310 protect the NFC operationalcomponents from high voltages received at antenna circuit 102. Forexample the regulator may limit the voltage to 3.3 or 1.8 voltsdependent on the voltage tolerance of the NFC operational components.Any suitable regulator and rectification circuit can be used for this.The NFC operational components may also include an amplifier foramplifying an RF signal inductively coupled to the antenna circuit 102.

In addition the NFC operational components include components forenabling modulation of an RF signal to enable data to be communicated toanother near field RF communicator in near field range of the NFCcommunicator 100 a. The data to be communicated is provided fromcontroller 107 to modulator 117 and as shown in FIG. 2, modulator 117 isarranged to control regulator 310 to modulate the effective impedance ofthe antenna circuit 102 in order to load modulate an RF H-fieldinductively coupled to the antenna circuit 102. Drive elements are alsoprovided for providing a modulated RF signal to the antenna thesecomponents comprise a signal generator 109 coupled via a driver 111 tothe antenna circuit 102. In this example, the signal generator 109causes modulation by gating or switching on and off the RF signal inaccordance with the data to be communicated. The NFC communicator mayuse any appropriate modulation scheme that is in accordance with thestandards and/or protocols under which the NFC communicator operates. Asanother possibility a separate or further signal controller may beincorporated within the NFC operational components to control modulationof the signal generated by the signal generator 109 in accordance withdata or instructions received from the controller 107.

The NFC operational components also include a controller 107 forcontrolling overall operation of the NFC communicator. The controller107 is coupled to a data store 108 for storing data (information and/orcontrol data) to be transmitted from and/or data received by the NFCcommunications enabled device. The controller 107 may be a controller ofa host device and/or a microprocessor, for example a RISC processor orother microprocessor or a state machine. Program instructions forprogramming the controller and/or control data for communication toanother near field RF communicator may be stored in an internal memoryof the controller and/or the data store.

The NFC communicator 100 a may operate in an initiator mode (that is asan initiating near field RF communicator) or a target mode (that is as aresponding near field RF communicator), dependent on the mode to whichthe NFC communicator is set. The mode may be determined by thecontroller 107 or may be determined in dependence on the nature of areceived near field RF signal. When in initiator mode, an NFCcommunicator initiates communications with any compatible respondingnear field RF communicator capable of responding to the initiating NFCcommunicator (for example an NFC communicator in target mode or an RFIDtag or transponder) that is in its near field range, while when intarget mode an NFC communicator waits for a communication from acompatible initiating near field RF communicator (for example an NFCcommunicator in initiator mode or an RFID initiator or transceiver). Asthus used, compatible means operable at the same frequency and inaccordance with the same protocols, for example in accordance with theprotocols set out in various standards such as ISO/IEC 18092, ISO/IEC21481, ISO/IEC 14443 and ISOIIEC 15693. NFC communicators commonlyoperate at or around 13.56 MHz.

When in initiator or target mode, the NFC communicator may communicatein accordance with an active or passive protocol. When using an activeprotocol the initiating NFC communicator will transmit an RF field andfollowing completion of its data communication, turn off its RF field.The responding near field RF communicator (target) will then transmitits own RF field and data before again turning off the RF field and soon. When using a passive protocol the NFC communicator (initiator) willtransmit and maintain its RF field throughout the entire communicationsequence. The protocol used will depend on instructions received fromthe controller 107 and the response received from a responding nearfield RF communicator.

In FIG. 2 control of operation of the NFC communicator is throughcontroller 107. As another possibility where the NFC communicator iscomprised as part of a host device, control of the operation of the NFCcommunicator may be directed by the host device, for example throughother functionality 105. In such circumstances all or part of thecontrol may be provided by other functionality 105. For example the NFCcommunicator controller 107 may control modulation and modulationprotocols whereas the data to be transmitted may be directed by the hostdevice through other functionality 105 or through controller 107. Inthese circumstances the voltage levels of the modulation signal are setby the host device.

The NFC communicator also comprises an antenna circuit 102. The designof the antenna circuit will depend on the NFC communicator 100 and theenvironment in which it operates. For example the antenna circuit may bein the form described for co-pending international patent applicationnumber PCT/GB2008/000992 (which claims priority from GB 0705635.1).

An example of a regulator that may be used in the NFC communicator suchas that shown in FIG. 2 will now be described with reference to FIG. 3.

FIG. 3 shows connection 202 is coupled via shunt element 201 a to groundor reference voltage connection 205 and via rectifying element 200 a andto resistance 210. Connection 203 is coupled via shunt element 201 b toground or reference voltage connection 205 and via rectifying element200 b to resistance 210. Resistance 210 couples the output of rectifyingelements 200 a and 200 b to resistance 212 which couples resistance 210to ground or reference connection 205. The two resistances 210 and 212are arranged as a potential divider between the rectifier output voltageVDD and ground 205. Amplifier 215 has first and second inputs 215 a and215 b. The first amplifier input 215 a is coupled to the rectifieroutput voltage VDD by resistance 210 and to ground or reference voltageconnection 205. Second amplifier input 215 b is coupled to a modulator117. Modulator 117 is arranged to receive a control signal fromcontroller 107 of the near field communicator. Amplifier output 215 c iscoupled to provide a control voltage for controlling shunt elements 201a and 201 b. Clock deriver 115 is coupled between connections 202 and203.

Rectifying elements 200 a and 200 b are components of a rectifier 200arranged to provide a rectified voltage VDD. Modulator 117 is arrangedto provide either a first voltage V1 or a second voltage V2 to thesecond amplifier input 215 b and thereby to control the output of theamplifier based on the rectified voltage VDD. In the example of FIG. 3an arrangement of switches is arranged to provide this function however,as will be appreciated, this control can be achieved by any otherappropriate means such as, for example, a level shifter or pulsegenerator. In operation connections 202 and 203 are coupled to receiveRF voltages TX1 TX2 from an inductive coupler (FIG. 2) such that shuntelements 201 a and 201 b represent an impedance load coupled in parallelwith the inductive coupler. Varying the impedance of shunt elements 201a and 201 b causes the load on the inductive coupler to be varied toprovide modulation of an H-field coupled to the inductive coupler.

Rectifying elements 200 a and 200 b provide a rectified voltage VDDwhich is coupled to resistance 210 to provide an input voltage toamplifier input 215 a. Modulator 117 is arranged to provide either afirst voltage V1 or a second voltage V2 to the second amplifier input215 b and thereby to control the output of amplifier 215 based on therectified voltage VDD. In operation the voltage at the amplifier output215 c will control shunt elements 201 a and 201 b such that, if VDDexceeds the voltage at amplifier input 215 b the shunt elements arebiased into a conducting state to reduce the voltage at TX1, TX2 (andthus VOD) until the voltages at amplifier inputs 215 a, 215 b areequalised.

As will be appreciated varying the voltage at amplifier input 215 bindirectly varies the load on an inductive coupler coupled between 202and 203 and therefore can provide load modulation of an RF H-fieldinductively coupled to said inductive coupler.

In operation, when an RF voltage is received at by the antenna circuit102 clock deriver 115 operates to derive a clock signal from the RFvoltage which is used in modulation and demodulation functions of theNFC communicator. In order to communicate data by modulation of thereceived RF signal a modulation signal provided by controller 107 iscoupled to modulator 117. Modulator 117 controls amplifier input 215 bto vary between first and second voltage levels V1 and V2 which areselected in accordance with the parameters of the NFC operationalcomponents. In the example of FIG. 3, modulator 117 employs anarrangement of switches to switch the amplifier input 215 b between thefirst and second voltage levels, V1 and V2. The modulator can include aband gap reference voltage and a voltage divider to divide the band gapvoltage to provide the first and second voltage levels. The second(upper) voltage level is selected according to the over upper voltagelimit of the silicon and the first (lower) voltage level is selectedbased on the minimum operating voltage of the clock deriver 115. Theclock deriver 115 can comprise a voltage comparator and the minimumoperating voltage of the clock deriver 115 is based on the minimumvoltage resolvable by the comparator. However often a received RF signalis subject to noise and the minimum operating voltage of a clock derivermay be set by the noise on the received RF signal and/or the signal tonoise ratio in order to achieve an acceptable accuracy/error rate of theclock signal.

Optionally, the modulator 117 is arranged to control the output ofamplifier 215 by providing a constant voltage to amplifier input 215 band to control the impedance of one or both of resistances 210 and 212such that the RF signal is regulated/modulated as set out above.

In this way the NFC operational components are protected from overvoltage conditions, load modulation and regulator function can beprovided using a small number of components and the NFC communicator canoperate reliably even when the data modulation signal is provided by acontroller of a host device (or designed according to differentprocesses) without compromising operation of the clock deriver 115.

The above embodiments are to be understood as illustrative examples ofthe invention. Further embodiments of the invention are envisaged. It isto be understood that any feature described in relation to any oneembodiment may be used alone, or in combination with other featuresdescribed, and may also be used in combination with one or more featuresof any other of the embodiments, or any combination of any other of theembodiments. Furthermore, equivalents and modifications not describedabove may also be employed without departing from the scope of theinvention, which is defined in the accompanying claims.

What is claimed is:
 1. A near field communication (NFC) device,comprising: a controller configured to provide data to be communicatedto a second NFC device; and a regulator, having a first shunt elementand a second shunt element, configured to: adjust an impedance of anantenna circuit in accordance with the data to load modulate a radiofrequency (RF) signal inductively coupled onto to the antenna circuit bythe second NFC device, and regulate a voltage induced in the antennacircuit by the RF signal, wherein the first and the second shuntelements are arranged to be in parallel with the impedance of theantenna circuit and are configured to be adjusted in accordance with thedata to adjust the impedance of the antenna circuit.
 2. The NFC deviceof claim 1, further comprising: a data store, coupled to the controller,configured to provide the data.
 3. The NFC device of claim 1, whereinthe NFC device is implemented as part of a host device, the host devicebeing configured to provide the data.
 4. The NFC device of claim 1,further comprising: a modulator, coupled to the controller, configuredto provide a modulation signal to the regulator to cause the regulatorto adjust the impedance of the antenna circuit.
 5. The NFC device ofclaim 4, wherein the modulator comprises: a first switch coupled to afirst voltage level; and a second switch coupled to a second voltagelevel, wherein the first switch is activated and the second switch isdeactivated when the data is at a first level to provide the firstvoltage level as the modulation signal, and wherein the first switch isdeactivated and the second switch is activated when the data is at asecond level to provide the second voltage level as the modulationsignal.
 6. The NFC device of claim 1, wherein the first shunt element iscoupled between a first terminal of the antenna circuit and a commonconnection, and wherein the second shunt element is coupled between asecond terminal of the antenna circuit and the common connection.
 7. TheNFC device of claim 1, wherein the regulator is configured to regulatethe voltage induced between a first terminal and a second terminal ofthe antenna circuit by the RF signal.
 8. A near field communication(NFC) device, comprising: a controller configured to provide first datato be communicated to a second NFC device in a first mode of operationand to receive second data communicated by the second NFC device in asecond mode of operation; and a regulator, having a first shunt elementand a second shunt element, configured to: adjust an impedance of anantenna circuit in accordance with the first data to load modulate aradio frequency (RF) signal inductively coupled onto to the antennacircuit by the second NFC device in the first mode of operation,regulate a voltage induced in the antenna circuit by the RF signal, andprovide the regulated voltage for demodulation to extract the seconddata from the regulated voltage in the second mode of operation, whereinthe first and the second shunt elements are arranged to be in parallelwith the impedance of the antenna circuit and are configured to beadjusted in accordance with the first data to adjust the impedance ofthe antenna circuit in the first mode of operation.
 9. The NFC device ofclaim 8, further comprising: a demodulator configured to: demodulate theregulated voltage to extract the second data in the second mode ofoperation, and provide the second data to the controller for processingin the second mode of operation.
 10. The NFC device of claim 8, furthercomprising: a modulator, coupled to the controller, configured toprovide a modulation signal to the regulator to cause the regulator toadjust the impedance of the antenna circuit in the first mode ofoperation.
 11. The NFC device of claim 10, wherein the modulatorcomprises: a first switch coupled to a first voltage level; and a secondswitch coupled to a second voltage level, wherein the first switch isactivated and the second switch is deactivated when the first data is ata first level to provide the first voltage level as the modulationsignal in the first mode of operation, and wherein the first switch isdeactivated and the second switch is activated when the first data is ata second level to provide the second voltage level as the modulationsignal in the first mode of operation.
 12. The NFC device of claim 8,wherein the regulator is configured to regulate the voltage inducedbetween a first terminal and a second terminal of the antenna circuit bythe RF signal.
 13. A method for communication in a near fieldcommunication (NFC) device, comprising: generating data to becommunicated to a second NFC device; generating a modulation signal toadjust an impedance of the NFC device, the generating comprising:activating a first switch of the NFC device and deactivating a secondswitch of the NFC device when the data is at a first level to provide afirst voltage level as the modulation signal, and deactivating the firstswitch and activating the second switch when the data is at a secondlevel to provide a second voltage level as the modulation signal; andsimultaneously adjusting the impedance of the NFC device in accordancewith the data to load modulate a radio frequency (RF) signal inductivelycoupled onto to the NFC device by the second NFC device and regulating avoltage induced in the NFC device by the RF signal.
 14. The method ofclaim 13, wherein the simultaneously adjusting comprises: simultaneouslyadjusting the impedance of the NFC device in accordance with the data toload modulate the RF signal in a first mode of operation, and furthercomprising: extracting second data from the regulated voltage in asecond mode of operation.
 15. The method of claim 14, wherein theextracting comprises: demodulating the regulated voltage to extract thesecond data in the second mode of operation.
 16. The method of claim 13,wherein the simultaneously adjusting comprises: simultaneously adjustingthe impedance of the NFC device in accordance with the data to loadmodulate the RF signal in a first mode of operation, and furthercomprising: switching on and off a second RF signal in accordance withthe data in a second mode of operation; and generating a magnetic fieldusing the switched second RF signal to communicate the data to thesecond NFC device in the second mode of operation.
 17. The method ofclaim 13, further comprising: deriving a clock signal from the RFsignal.